Airbag arrangement for a steering column or dashboard

ABSTRACT

In an air-bag arrangement in a motor vehicle a gas generator ( 5 ) has a flange ( 8 ) which is spaced from a flange member ( 3 ) by elongate spacer elements ( 9 ). The spacer elements pass through apertures ( 20, 21 ) formed in an air-bag adjacent a central aperture ( 19 ). On inflation of the air-bag, the part of the air-bag surrounding the aperture will be drawn into an engagement with the flange ( 8 ). Should a very high pressure exist within the air-bag, the part of the air-bag surrounding the aperture will be driven away from the flange ( 8 ), with part of the aperture sliding along the elongate elements ( 9 ), thus permitting excess pressure to be relieved.

BACKGROUND OF THE INVENTION

1. Field of the Invention

THE PRESENT INVENTION relates to an air-bag arrangement for a motorvehicle and more particularly relates to an air-bag arrangement suitablefor mounting in front of an occupant of the motor vehicle in thesteering column or the dashboard of the vehicle.

2. Description of Related Art

It is known to mount an air-bag and a gas generator arrangement in frontof an occupant of the motor vehicle such that in an accident situation,the gas generator will inject gas into the air-bag to inflate theair-bag. Thus, as the torso and head of the occupant move forwardrapidly, the inflated air-bag provides a cushioning effect to reduce orminimise injury to the occupant of the vehicle.

However, a problem arises with such prior air-bag arrangements when theoccupant of the vehicle is not fully sitting back in the vehicle seat.For example the occupant of the vehicle may be leaning forward to obtainan item from the glove compartment or may, for any other reason, besitting forwardly of the seat such that his head and upper torso isrelatively close to the air-bag arrangement.

If an occupant of the vehicle is leaning forwardly relative to thenormal position of an occupant of the seat, the rapidly inflatingair-bag will impact with the occupant and further inflation of theair-bag will be resisted or prevented. Consequently the gas pressurewithin the air-bag will increase to a level much greater than thatexperienced during unimpeded inflation of the air-bag. Consequently highforces will be exerted on the part of the occupant adjacent the air-bag,which may lead to serious injuries. It is therefore desirable, afterpart of the occupant has impacted with the air-bag, to reduce gaspressure within the air-bag and consequently to reduce the force exertedby the inflating air-bag on the part of the occupant of the vehicle.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved air-bag arrangement.

According to the present invention there is provided an air-bagarrangement for a motor vehicle comprising an air-bag, a gas generatorhaving a flange member and an apertured base plate member spaced apredetermined distance away from the flange member, elongate elementsbeing provided extending between the flange member and the base platemember, the air-bag having an opening forming a throat, the air-bag alsohaving a plurality of apertures surrounding said opening, each aperturereceiving a respective said elongate element the arrangement being suchthat, in an accident situation, as gas from the gas generator isintroduced to the air-bag, a part of the air-bag adjacent the openingmoves into substantially sealing engagement with the flange member ofthe gas generator and such that, if the inflating air-bag impacts withan occupant of the vehicle, increasing gas pressure within the air-bagmoves the part of the air-bag surrounding the opening towards the baseplate member so that gas flows from the air-bag through a gas flow pathdefined at least partly by the space between the flange member and thebase plate member.

Preferably the elongate elements comprise elongate studs each having alarge diameter region inserted through a respective aperture in theair-bag, and a smaller diameter terminal region inserted in an apertureformed in the base plate member. Each stud serves as a spacer betweenthe flange member and the base plate member.

Conveniently each stud is provided with a screw thread on which a nut issecured.

In one embodiment the elongate elements comprise studs and each studpasses through a bush which serves as a spacer between the flange memberand the base plate member.

Alternatively the elongate elements comprise tabs which extend from onemember to the other member.

Alternatively the elongate elements comprise protrusions extending fromone member to the other, the protrusions serving as spacers between theflange member and the base plate member.

Preferably each protrusion defines an aperture through which arespective stud is inserted.

Preferably the throat is dimensioned to receive part of the gasgenerator.

Conveniently the throat is reinforced with an additional layer ofmaterial.

Advantageously the additional layer of material is formed of a fabric.

Alternatively the additional layer of material is formed of metal.

Alternatively the additional layer of material is formed of a plasticsmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, and so thatfurther features thereof may be appreciated, the invention will now bedescribed, by way of example, with reference to the accompanyingdrawings in which:

FIG. 1 is an exploded perspective view of the air-bag arrangement of thecurrent invention;

FIG. 2 is a sectional view of the air-bag arrangement taken on line A—Aof FIG. 1 showing the air-bag arrangement in a first condition; and

FIG. 3 is a sectional view corresponding to FIG. 2 but showing theair-bag arrangement in a second condition.

DETAILED DESCRIPTION OF THE INVENTION

An air-bag arrangement 1 comprises a gas generator 2, a base platemember 3 and an air-bag 4.

The gas generator 2 comprises a cylindrical housing comprising an uppercircular end 5 and a lower circular end 6 interconnected by a tubularside wall 7. A substantially square flange member 8 extends radiallyfrom and surrounds the tubular side wall 7 and separates the firstcircular end 5 from the second circular end 6. The flange member 8 isprovided with four elongate elements in the form of studs 9 which aresubstantially equispaced about the flange member 8. The studs 9 extendfrom the side of the flange member 8 closest to the second circular end6 in a direction parallel to the tubular side wall 7 of the gasgenerator 2.

Each stud 9 has two regions of different diameter. The region 10 of eachstud 9 closest to the flange member 8 has a relatively large diameterand the region 11 of each stud 9 remote from the flange member 8 has arelatively small diameter. The small diameter region 11 is provided witha screw thread.

Four tabs 12 also extend from the side of the flange member 8 closest tothe second circular end 6 in a direction parallel to the tubular sidewall 7. Two tabs 12 are located on one part of the flange member 8between two of the studs 9 and the other two tabs 12 are located on anopposing part of the flange member between the other two studs 9.

The base plate member 3 comprises a substantially square plate ofuniform thickness. The base plate member 3 has a centrally locatedcircular aperture 13 dimensioned to receive the second circular end 6 ofthe gas generator 2. The upper surface of the base plate member 3extends around the circular aperture 13 and is provided with fourprotrusions 14 which extend upwardly and substantially perpendicularlyfrom the upper surface of the base plate member 3. Each protrusion 14 isprovided with an axial bore 15 which extends through the protrusion 14and through the base plate member 3. Each bore 15 is dimensioned andlocated to receive the smaller diameter region 11 of a respective stud9. The upper surface of the base plate member 3 is also provided withfour recesses 16 each dimensioned and located to receive a lower portionof a respective tab 12.

The air-bag 4 comprises two fabric layers 17 and 18, each fabric layer17 and 18 comprising a circular disc of fabric. The layers of fabric 17and 18 are superimposed and are connected at their peripheries, forexample by a seam. The lower fabric layer 17 is provided with acentrally located circular opening 19 forming a throat. The circularopening 19 is dimensioned and located to receive the lower circular end6 of the gas generator 2. Four apertures 20 are formed in the firstfabric layer 17 and are equispaced about the periphery of the opening19. The four apertures 20 are dimensioned and located such that bothregions 10 and 11 of each stud 9 may be inserted through a respectiveaperture 20. Four further apertures 21 are also provided about theperiphery of the opening 19 and are dimensioned and located such thatpart of each tab 12 may be inserted through a respective furtheraperture 21.

In assembling the air-bag arrangement, the gas generator 2 will beinserted through the opening 19 of the first fabric layer 17 so that thegas generator 2 is located within the interior of the air-bag 4. The gasgenerator 2 will be aligned with the first fabric layer 17 such thateach stud 9 will be inserted through a respective aperture 20 of thefirst fabric layer 17 and such that each tab 12 will be inserted througha respective further aperture 21 of the first fabric layer 17. Thesecond circular end 6 of the gas generator 2 may protrude through theopening 19 in the air-bag 4.

The gas generator 2 and the air-bag 4 will then be offered to the baseplate member 3, the base plate member 3 being orientated such that thesmaller diameter region 11 of each stud 9 may be inserted through arespective bore 15 on the base plate member 3. It is to be appreciatedthat, when so inserted, part of the smaller diameter region 11 of eachstud 9 will extend beneath the lower surface of the base plate member 3and a nut 22 will be screwed onto the screw thread provided on therespective lower region 11 of the respective stud 9. Each tab 12 will bereceived within a respective recess 16 on the base plate member 3. Thusthe first fabric layer 17 of the air-bag 4 will be sandwiched betweenthe flange member 8 of the gas generator 2 and the base plate member 3.It is to be appreciated that the larger diameter region 10 of each stud9 will space the flange member 8 of the gas generator 2 a predetermineddistance from the base plate member 3. It is also be appreciated thatthe tabs 12 will also assist in spacing the flange member 8 of the gasgenerator 2 and the base plate member 3 the same predetermined distanceapart. It is envisaged that the predetermined distance apart will bebetween 2 millimetres and 10 millimetres.

It is to be further appreciated that, when the above arrangement isassembled as has been described, the apertures 20 and further apertures21 provided around the periphery of the opening 19 of the fabric layer17 of the air-bag 4 are permitted to slide along the studs 9 and thetabs 12 respectively. Thus the part of the first fabric layer 17 of theair-bag 4 adjacent to the opening 19 may move from a position adjacentthe flange member 8 of the gas generator 2 to a position adjacent thebase plate member 3.

Referring now to FIG. 2, in an accident situation, gas will be injectedfrom the gas generator 2 into the air-bag 4 in a direction substantiallyas shown by arrow 23. This direction of flow of gas from the gasgenerator 2 will give the entire air-bag momentum in the direction shownby the arrow 23 and the first fabric layer 17 will be moved along thestuds 9 and tabs 12 to a position adjacent and firmly in contact withthe flange member 8 of the gas generator 2. It is to be appreciated thatwhen the fabric layer 17 of the air-bag 4 is in this position, theair-bag 4 is substantially sealed and gas from the gas generator 2 willremain substantially in the air-bag 4. Thus the air-bag will inflate ina conventional manner.

If an occupant of the vehicle is leaning forwardly of the vehicle seatand is thus relatively close to the inflating air-bag 4, the inflatingair-bag 4 will impact with part of the occupant of the vehicle prior tothe air-bag 4 being fully inflated. Further inflation of the air-bag 4in the direction of the arrow 23 in FIG. 2 will be prevented orrestricted and thus gas pressure within the air-bag 4 will increase. Theincreasing gas pressure within the air-bag 4 will move the part of theair-bag 4 adjacent the opening 19 away from sealing engagement with theflange member 8 of the gas generator 2 to a position adjacent base platemember 3. This movement will be enabled by the apertures 20 and furtherapertures 21 sliding along the larger diameter region 10 of the studs 9and along the tabs 12 receptively. This is the position shown in FIG. 3.

When the part of the fabric layer 17 adjacent the opening 19 is in theposition shown in FIG. 3, it is to be appreciated that gas may flow fromthe air-bag through a gas flow path defined by the space between theflange member 8 of the gas generator 2 and the base plate member 3, theopening 19 in the air-bag 4 and the aperture 13 in the base plate member3. This gas flow path is shown by arrows 24. This flow of gas from theair-bag will reduce the gas pressure within the air-bag 4 and thus theforce exerted by the inflating air-bag 4 on the part of the occupant ofthe vehicle in contact with the air-bag 4 will be regulated. It isenvisaged that this regulation of force will greatly reduce the risk ofinjuries being imparted to the occupant by the inflating air-bag 4.

It is to be appreciated that, in an alternative embodiment, the spacingbetween the flange member 8 of the gas generator 2 and the base platemember 3 may be effected solely by the studs 9, with the tabs 12 beingomitted, or solely by the tabs 12, with the studs being of uniformsection along their length. The tabs may be on the base plate member 3instead of being on the flange member 8.

In a further alternative embodiment each stud 9 comprises a standardbolt of constant diameter which is inserted in a bush prior to beingsecured to the base plate member 3. The bushes serve to space the gasgenerator 2 and the base plate member 3 the predetermined distanceapart.

In a further alternative embodiment, each protrusion 14 serves as aspacer between the flange member 8 and the base plate member 3. Eachstud 9 comprises a standard bolt of constant diameter which is insertedin a respective aperture 15 formed in each protrusion 14. When assembledas has been described above, the part of the fabric layer 17 which formsthe periphery of each aperture 20 is clamped between the flange member 8and a respective protrusion 14. Thus, in an accident situation, the partof the air-bag between each protrusion 14 in an accident situation willmove from a position adjacent the flange member 8 to a position adjacentthe base plate member 3 to allow gas to flow out of the air-bag.

Further, it is envisaged that the periphery of the opening 19 formingthe throat of the first fabric layer 17 could be reinforced with anadditional layer of material. Such a material could be formed from afabric, a plastic or a metal material.

In the present Specification “comprises” means “includes or consists of”and “comprising” means “including or consisting of”.

1. An air-bag arrangement for a motor vehicle comprising an air-bag, agas generator having a flange member and an apertured base plate memberspaced a predetermined distance away from the flange member, elongateelements being provided extending between the flange member and the baseplate member, the air-bag having an opening forming a throat, theair-bag also having a plurality of apertures surrounding said opening,each aperture receiving a respective said elongate element, thearrangement being such that, in an accident situation, as gas from thegas generator is introduced to the air-bag, a part of the air-bagsurrounding the opening moves into substantially sealing engagement withthe flange member of the gas generator and such that, if the inflatingair-bag impacts with an occupant of the vehicle, increasing gas pressurewithin the air-bag moves the part of the air-bag surrounding the openingtowards the base plate member so that gas flows from the air-bag througha gas flow path defined at least partly by the space between the flangemember and the base plate member.
 2. The arrangement of claim 1 whereinthe elongate elements comprise elongate studs each having a largediameter region inserted through a respective aperture in the airbag,and a small diameter terminal region inserted in an aperture formed inthe base plate member.
 3. The arrangement of claim 2 wherein each studis provided with a screw thread on which a nut is secured.
 4. Thearrangement of claim 1 wherein the elongate elements comprise studs andwherein each stud passes through a bush which serves as a spacer betweenthe flange member and the base plate member.
 5. The arrangement of claim1 wherein the elongate elements comprise tabs which extend between theflange member and the base plate member.
 6. The arrangement of claim 1further comprising protrusions extending between the base plate memberand the flange member, the protrusions serving as spacers between theflange member and the base plate member.
 7. The arrangement of claim 6wherein each protrusion defines an aperture through which a respectivestud is inserted.
 8. The arrangement of claim 1 wherein the throat isdimensioned to receive part of the gas generator.
 9. The arrangement ofclaim 1 wherein the throat is reinforced with an additional layer ofmaterial.
 10. The arrangement of claim 9 wherein the additional layer ofmaterial is formed of a fabric.
 11. The arrangement of claim 9 whereinthe additional layer of material is formed of metal.
 12. The arrangementof claim 9 wherein the additional layer of material is formed of aplastics material.